Alignment and alignment dynamics of nematic liquid crystals on Langmuir-Blodgett mono-layers

Mono-layers of stearic and behenic acids, deposited with the Langmuir-Blodgett technique, were used as aligning films in nematic liquid crystal cells. During the filling process the liquid crystal adopts a deformed quasi-planar alignment with splay-bend deformation and preferred orientation along the filling direction. This state is metastable and transforms with time into a homeotropic state once the flow has ceased. The transition is accompanied by formation of disclination lines which nucleate at the edges of the cell. The lifetime of the metastable splay-bend state was found to depend on the cell thickness. On heating, an anchoring transition from quasi-homeotropic to degenerate tilted alignment in the form of circular domains takes place near the transition to the isotropic phase. The anchoring transition is reversible with a small hysteresis.